Ep 75: Hidden network: The evolutionary relationship between arbuscular mycorrhizal fungi and plants (with Toby Kiers)
What rules dictate trade in symbiosis? How did the complex relationship between plants and arbuscular mycorrhizal fungi evolve? What’s really going on in the world beneath our feet?
On this episode, we talk to Toby Kiers, an evolutionary biologist at VU University Amsterdam, about the massive networks of arbuscular mycorrhizal fungi (AMF) that inhabit the soil beneath our feet. Toby studies the symbiotic relationship between AMF and 80-90% of plant species, through which the tube-shaped fungi cells trade nutrients with plant roots in exchange for carbon. We draw connections between these networks and human networks, and discuss whether economists should be taking notes from these systems.
We also talk about SPUN, a non-profit initiative Toby’s group recently launched with the goal of mapping these fungal networks and advocating for their protection worldwide.
Cover photo: Keating Shahmehri
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SPEAKERS
Art Woods, Toby Kiers, Marty Martin
Art Woods 00:00
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Marty Martin 00:17
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Art Woods 00:29
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Marty Martin 00:34
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Art Woods 00:43
And now here's the show.
Marty Martin 00:51
As the year winds down, let's just say it was indeed another challenging one.
Art Woods 00:55
But Marty, it's been tough for the past 4 billion years or so, and it shows no sign of letting up.
Marty Martin 01:01
And that's why we all need a little help from our friends.
Art Woods 01:04
Or our symbionts. The history of life is characterized by major transitions, many of which revolve around the formation of cooperative relationships. Maybe the most obvious example is the origin of eukaryotes from bacterial and archaeal lineages getting together.
Marty Martin 01:19
Or think back to Episode 18 and the cicada bacteria relationships described by John McCutcheon
Art Woods 01:24
In some ways, cooperative systems like these are straightforward because the relationships become so tight that partners become inseparable, and essentially totally interdependent.
Marty Martin 01:34
In other systems, the relationships aren't as tight. The partners interact, and they can cooperate under the right conditions, but the interactions may not be obligate, and the details are updated continuously. They're ecologically and evolutionarily negotiable.
Art Woods 01:47
Think gut microbiomes, as we discussed in Episode 19, with Rob Dunn. Trillions of individual microbes from 1000s of species live in our guts, and they perform really key functions for us. Another example is cooperation between fungi and plant roots.
Marty Martin 02:02
Today's guest, Toby Kiers, is an evolutionary biologist at the Free University in Amsterdam, She studies the underground networks of arbuscular mycorrhizal fungi and their intimate interactions with plant roots. And her 2019 TED talk, she described the economics of this relationship, how each partner negotiates and trades with the other,
Art Woods 02:20
Or steals and borrows,
Marty Martin 02:21
All without brains or emotions.
Art Woods 02:24
Or lawyers or free trade agreements.
Marty Martin 02:26
This hidden economy trades resources across the globe, and it plays an important role in the health and well being of almost all terrestrial ecosystems.
Art Woods 02:34
A key trade in this relationship is carbon for nutrients. The partners trade resources that they can obtain easily for those that they cannot. Plants, for example, can access large amounts of energy from photosynthesis, which they put into carbon based molecules like sugars.
Marty Martin 02:49
But plants have a hard time extracting other nutrients like phosphorus and nitrogen from soil. By contrast, fungi excel at nutrient extraction, but they lack the energy to do it. So the key trade comes into focus. Plants provide carbon to the fungi in return for nutrients.
Art Woods 03:03
But just stating the fact of this exchange doesn't say much about the rules that shape it. How much carbon should a plant give its fungi per unit of phosphate delivered? And conversely, how much phosphate should the fungus give to the plant per unit of carbon delivered?
Marty Martin 03:17
And what if one partner cheats the other?
Art Woods 03:19
Another big question is how fungi should move nutrients through their networks whenever soil resources are patchily distributed,
Marty Martin 03:26
Which they pretty much always will be.
Art Woods 03:27
Should nutrients mined in rich patches be transported to poor patches? And how much more carbon can fungi get for nutrients delivered that way?
Marty Martin 03:35
Toby and her team are trying to answer these questions using a broad variety of approaches. One awesome experiment that we'll talk about during the show is a technique for visualizing flows of phosphorus in fungal hyphae.
Art Woods 03:45
They do it by tagging phosphate with what are called quantum dots, which can be made to fluoresce in different colors. This gives the team the means to visualize phosphate flows coming from multiple different sources at the same time, pretty great. They're using approaches like this to reveal the basic trade rules of the root fungus interactions.
Marty Martin 04:04
We also spoke to Toby about her new nonprofit called SPUN, the Society for the Protection of Underground Networks. Check out the website, www.spun.earth, to see some amazing videos of phosphate flowing through fungal hyphae. The site also lays out the ecological importance of fungal root networks and describes how climate change might affect them.
Art Woods 04:22
I'm Art Woods,
Marty Martin 04:23
and I'm Marty Martin,
Art Woods 04:24
and this is Big Biology.
Marty Martin 04:38
Toby, thank you very much for joining us on the show today. We're really excited to talk about the many projects that you're involved in right now. Before we get into the details of that science, we're curious about how you got into science in the first place. What were the formative early experiences that oriented you towards a career in science?
Toby Kiers 04:55
Well, first of all, thank you so much for having me. I'm a big fan of the show. And yeah, when you ask about sort of origin of science, probably well, I left university I left my undergrad university as I was getting my degree because I wanted to become a scientist so much that I thought it was easier to leave science and actually become a field biologist rather than go through the headache of getting a degree. So I left my undergraduate and traveled to the tropics where I was a fellow for a year in Panama, and I was already studying things under our feet.
Marty Martin 05:29
Okay, okay. What were you doing in Panama? That was, I guess, the STRI, Smithsonian Tropical Research Institute.
Toby Kiers 05:37
Exactly. I was on Barro Colorado at the time, and I was studying mycorrhizal networks. So these are these fungal networks that are in symbiosis with plant roots. And at the time, people were very interested in, you know, the diversity of plants above ground, but it was kind of a new frontier to look at the biodiversity below ground.
Marty Martin 05:58
So you you said you left science to get into science? What, would you give that advice to other students considering to go into biology? Or just generally, what kind of advice would you give students? You know, undergraduates thinking about graduate school or continuing in science?
Toby Kiers 06:11
Yeah, leaving science to go into science, I guess, is not the best idea.
Marty Martin 06:16
Atypical for sure.
Toby Kiers 06:17
Atypical. But you know, working with great scientists at a young age is definitely good advice. And that's what I was able to do by actually taking some time off when I was an undergrad, I was working with some really top scientists at a very early age. And of course, they were the ones that convinced me to go back and get a PhD and follow the normal route. But being exposed to such great thinkers in a in a field station capacity was fantastic.
Art Woods 06:43
So describe that, that normal route that you went back to so what did you do for grad school? And did you do postdocs and that kind of thing?
Toby Kiers 06:49
I did then it became very, very normal.
Art Woods 06:52
Very normal?
Toby Kiers 06:52
Exactly, exactly. Well I had to finish my undergrad. And then I went to UC Davis in the ecology program and was there for four years working with Ford Denison. And we were studying the evolution of cooperation between legumes and nitrogen fixing bacteria. So we were very interested in trying to understand how legumes control the growth of rhizobia on the root system. So these are bacteria that can fix atmospheric nitrogen, right. So the atmosphere is mostly made up of nitrogen, and rhizobia are very good at breaking that triple bond and making it into a form that plants can use a form of nitrogen that the plants can use. But they're not all as good as one another, and some actually try to divert energy from the plants and use it for their reproduction. So they store a lot more compounds and do not fix a lot of nitrogen. And you can imagine that that's a brilliant evolutionary strategy, especially if everybody else on the root system is busy fixing nitrogen, because then you have a healthy host, and you don't have to contribute to that. So we were really trying to understand how do legumes control the spread of these cheating type behaviors in rhizobia?
Art Woods 08:09
Let's turn now to some of your work on, other work on cooperations and symbioses. You've done this amazing set of things over the past few years, thinking about evolution of cooperation among different groups and the sorts of rules that structure those cooperations. And I want to start by asking you about a somewhat older paper of yours that was in PNAS in 2015. This, this paper focuses on major evolutionary transitions in life, which a number of scientists have thought about pretty intensively over the last the last century. And you make the argument and I think I agree that a lot of these major transitions in life can be traced to new and major cooperative events. So an example would be things like eukaryotic cells arising as cooperation between formal archaeal and bacterial lineages, and then that cooperation leading to some kind of explosion in diversity. But that's only one example among many, and I just want to ask, just sort of generally like what do you think are the conditions that promote that sort of cooperative behavior and coming together of formerly separate lineages?
Toby Kiers 09:13
So these transitions in what we call individuality, they're very rare, and they really require strict conditions. And the ones that interest me the most are when you have partners of different species. So again, if we're talking about symbiotic partnerships, and you have organisms that are exchanging resources, but are different species, and you can, even with the most sort of extreme examples of different species coming together, you can have these transitions in individuality. And I think that the two major conditions that you need or that the partner interests really need to be aligned, right? That sounds very simple, but over evolutionary time that can be difficult to achieve. And the second is that the benefits of this type of, let's call it integrated cooperation, they have to lead to mutual dependence. That means that both partners become so dependent on each other that actually the loss of autonomy, the loss of being an individual,
Art Woods 10:11
They can't go back.
Toby Kiers 10:12
Yeah, they can't go back that becomes more favorable.
Marty Martin 10:15
What are the conditions that promote the initial formation of cooperation? I mean, it's not the case, as I remember, in the paper, that cooperation is possible all the time, everywhere.
Toby Kiers 10:24
Exactly. So usually what what has to happen is that a benefit needs to come that is harder to gain than the individual can get themselves. So basically, you need to have a situation where you've got strict mutual dependence, that becomes beneficial. So usually, that only happens when one partner can access some form of energy or resources that the other doesn't have access to. And that really starts the kind of chain link formation of this type of mutual dependence.
Art Woods 10:59
So what are some other examples besides the evolution of eukaryotic cells that illustrate this process?
Toby Kiers 11:04
Well, usually we can see it very well, especially with symbioses, for example, insects, like let's take mealy bugs are a great example where they depend on bacterial endosymbionts for nutrient provisioning, right? They need some kind of nutrient provisioning. In this sense, even those endosymbionts themselves can actually harbor their own endosymbionts, right. So it becomes sort of a nested, if you will, process. But in this case, you can have similarities that almost it starts to resemble a host organelle. The dependence becomes so extreme, that it's not clear when the bacterial partnership left being an individual and became an organelle. Right? You've got similarities in genome size, encoding capacity, even the ability to import proteins that are produced by the host, which is, you know, kind of a characteristic of an organelle. And so it's become a big debate in the literature is like, at what point does an endosymbiotic become an organelle?
Art Woods 12:06
Yeah, that's, that's super interesting. We had a great conversation a couple years ago with a then-colleague of mine, a guy named John McCutcheon, who works on evolutionary trajectories of the sort that you just described. And he's especially interested in bacteriums, bacterial symbionts of cicadas and has used those as a model to think about the evolution of organelles like mitochondria and chloroplasts, because he's looking at sort of relatively new evolutionary associations and you know, they're not as ancient as chloroplasts or mitochondria, and yet they show a lot of this kind of similar pathways, right. So sort of genome reduction and extreme dependence of host and symbiont on on each other. I think it's just super interesting.
Toby Kiers 12:43
Yeah, I mean, so John, obviously, John McCutcheon's work is really, you know, he's just such a big leader in this field. And what's interesting is, I think, you know, one of the big questions has always been why do some partnerships become like physically and genomically and metabolically integrated, and others just don't, right? There's some hosts that evolve these extreme dependency on their symbionts. And others maintain facultative associations. So I think when we talk about those questions, this idea, this individuality idea, you know, it's also called the major transition approach, it's really focused on those cases where groups of individuals that yeah, they could previously replicate independently, they cooperate to form this new, even more complex organism, and trying to understand when hosts are under selection pressures for that, for that to happen and when not, when do they just maintain these facultative relationships, I think is one of the most interesting questions in evolutionary biology.
Marty Martin 13:40
Yeah, you know, I mean, maybe this is a giant question that's, it's just too big for us to be able to say a ton about but I'm obviously intrigued by the coming together of these different lineages and how that's, and the doors that opens as far as diversification and size, we haven't hit that one, but that's a conspicuous one as well. What about the problem of regulation, though? I mean, how, how does, is there any sort of consistency in the steps by which two different lineages become integrated? Cause it's pretty difficult to maintain life in a single organism, right? Whn you put two things together, there's conflict, and then there's the opportunities. How do we think about that? What's the sort of most active research in that area now?
Toby Kiers 14:23
I think it's interesting to think about when these, when there is no major transition, it's likely because the host is generally working simultaneously with multiple genotypes. That is very hard in terms of trying to reduce conflict. And this can be positive for the host, right? I mean, imagine if you're a host and you're working with multiple genotypes simultaneously, you can exploit a much wider range of environmental conditions, right? It increases your potential for conflict among those competing symbionts, but it also gives you an ability to exploit this wider range. So for example, when I talked about legumes and rhizobia, those rhizobia aren't, you know, we're not talking about those two partners coming together to form a new individual. There's some selection pressures that actually favor them not coming together as one individual, and likely that's because the benefits of the partnership vary with environmental context, right. So as soon as you've got a variation in environmental context, let's say there's a high nitrogen availability in the soil, and it's cheaper to get nitrogen directly from the soil than from an endosymbiont, then you're going to tend to want to be able to get nitrogen that way. So again, it's this question of how much variation is there in environmental contexts? And how does the benefits of those partnerships vary with that context?
Art Woods 15:43
And so to be clear, if the plants in that example you just gave, if they find themselves in high nitrogen soil, then they just kick the rhizobia out and get their nitrogen directly from the soil?
Toby Kiers 15:52
Exactly, exactly. So they've evolved ways to have, you know, very intense sensing mechanisms for levels of nitrogen. And so yeah, when there's high nitrogen soils, then they're not going to put energy into supporting these nitrogen fixing symbionts. And, of course, the one of the cool things that happens with these hosts is that they've they, you know, if, if that happens that they always have to be determining the cost and benefit, this cost benefit analysis of actually interacting with the symbiont, hosts evolve incredible ways of interacting with those symbionts. So for example, with the legume rhizobia symbiosis, what we learned is that, if the rhizobia failed to provide nitrogen, then the legumes actually suffocate them, they cut off their oxygen supply, and reduce the fitness of those bacteria. So again, you've got all of these partnerships, but as long as there's some kinds of variation in the environment, it's going to lead to different selection pressures.
Art Woods 16:50
So maybe what you just said answers this, but it feels like in these systems, it would be very easy, at least at some points for one partner to really exploit the other, and, you know, become a drag, I guess, if we think about the microbes exploiting the hosts, then that's almost as if they're becoming a disease instead of a symbiont. And I mean, is it true that, for example, if the host is dealing with lots of genotypes of a microbe that some of those genotypes may evolve to be selfish and exploitative? Is that one of the risks of dealing with multiple genotypes?
Toby Kiers 17:24
That's a huge risk, right? So we just had a paper out, I think it was last year, looking at yeah, across all of these different beautiful host symbiont relationships, you know, are there sort of key takeaways for how hosts are, who are facing these issues, deal with this variation, and one of the things that we see across the tree of life is that hosts tend to evolve compartments that allow them to spatially separate these genotypes in a way that allows them to discriminate amongst them. If they're all mixed, let's say, in one area, it's very hard not only to discriminate who's doing what, who's doing well, and who's doing poorly, but it's also hard to, you know, control the reproductive success of those genotypes. As soon as you have different compartments, you've solved that problem. And so we see that not only in legumes, but we see it in squid systems, right? What also have these light producing bacteria. But because of these compartments, the host can tell which bacteria are producing light and which ones aren't. And they can expel the ones that are poor symbionts. So compartmentalization is something that we see again and again, across the tree of life in terms of being able to control symbionts.
Art Woods 18:41
Yeah, that's super cool, because it feels like that would also be a mechanism for them to be able to exploit the genetic diversity of the microbes and gain those benefits of having a wider range of metabolic inputs while still controlling who's getting their own resources, right?
Toby Kiers 18:55
Exactly. It's very simple, it's very elegant, and it's expensive, right? So you know, making these compartments can be expensive, but it allows you a very precise level of control in terms of who and when you interact with those symbionts. Right, it's not just who, but when, when you need the symbionts and when you don't.
Marty Martin 19:16
So Toby, I find the upstream part of this super compelling because the host has to find these other organisms, distinguish these organisms from something else, and then employ different strategies for each one of them, presumably, depending on what they are. As cool as I find that I'm gonna let that go, because what you just said is even more interesting, if you, well especially if you can offer an example about well what I'm hearing is a toolkit that you've got these different genotypes that are left to be hanging around, presumably, the host could get rid of some fraction if they didn't want them, but do you have an example where a plant or whatever it might be is employing these different groups depending on context, am I understanding you right?
Toby Kiers 19:58
Yeah, I mean, that's, you know, you're asking for a hard example, but I think I have one. I mean, these are very different compartments, though, right? So I'm not quite sure if, if this will answer your question, but let me try. Let's take a plant as a great example, because on the one hand, it needs nitrogen, and in legumes, they evolved these nodules that house rhizobia that provide the perfect conditions for them to fix nitrogen. But at the same time, they're also interacting with mycorrhizal fungi, which are also endosymbionts, right? These fungi are penetrating into cells and forming structures for trade. And depending on what kind of, and providing lots of phosphorus, so I didn't say that. So the fungus is growing out into the soil, foraging for all different kinds of nutrients, but generally bringing back nitrogen and phosphorus. So again, you can play with this type of tripart mutualism, as it's called, to think about these different compartments, and which ones are more important under what conditions. So again, it's two very different types of compartments, but they're providing different resources, and the host has to be able to discriminate among them. And in the case of the arbuscule, it's providing sugars and fats to the fungi in a very ephemeral structure called the arbuscule, which then collapses after six or seven days and forms in a new compartment. So it's a very, very dynamic situation, and you can imagine that the host, over you know hundreds of millions of years of evolution, especially with the fungi has become very good at discriminating between fungi that are providing lots of nutrients and those that aren't, but it needs these different types of compartments to get at these different types of resources.
Marty Martin 21:41
That's fascinating.
Art Woods 21:42
Wow, that's super cool. As you're saying this, I'm having this vision of the host kind of being in control, right? It's got these two different kinds of symbionts and it's somehow orchestrating interactions. But couldn't you also imagine that the two different microbial, fungal and microbial symbionts you know, are establishing their own rules and their own ways of interacting within the environmental context of being together inside this thing, this host that is the plant.
Toby Kiers 22:06
Definitely. So I'm glad that we got to this fast enough, because this is exactly how our labs study these types of interactions, as actually not from the host point of view, but from the microbial point of view. So we're really interested in trying to understand the strategies that these microbes have evolved to be able to maximize the amount that they get from the hosts. And wow, they can do some really creative things in terms of you know, even we can even use the word arms race, if you will, right, in terms of the host controlling how much resources go to these symbionts, but then the symbionts evolving really fantastic ways of manipulating the host that really allow them to maximize the amount that they're getting from that partnership.
Marty Martin 22:52
Something that I think you mention in the 2015 paper is the honesty of these signals that host and microbes are using. How much do we know about the cheating that goes on via these different signals that are being used? That seems like a low hanging fruit to be exploited for opportunity?
Toby Kiers 23:09
Yeah, definitely. And so that's why when we do talk about, we do talk about the symbioses, where we tend not to actually focus so much on signals, because signals can evolve, and then they can mean different things, and then they can be used for different, they can be co opted. But when we look at how the hosts and these microbes tend to interact, it's usually based on the actual exchange of resources. So it's not a signal unnecessarily attached to the resources, but it's a signal of the resources themselves. So again, it's the actual nitrogen, it's the actual phosphorus that's coming through, because many different microbes can evolve a way of saying I'm a good, I'm a good partner. And so for example, when we look at the legume rhizobia symbiosis, we call it kind of a two sieve process, right? The first sieve is what we call partner choice, and that sort of this back and forth between the plants and the rhizobial strain to see, okay, is it a compatible match? Is this going to form an actual nodule? But once the nodule is formed, that's when the honesty comes in. Because that is when it is solely about the resource, level of resource exchange.
Art Woods 24:19
Yeah, that totally makes sense. So you're saying that the thing that's getting traded is not information, it's the actual thing, the currency that matters? And so it's like totally honest, because that's all there is.
Marty Martin 24:30
No, IOUs, the real deal.
Art Woods 24:39
Well, hey, we want to turn even more broadly to talking about AMF, arbuscular mycorrhizal fungi, and maybe can you just give our listeners like a one minute summary of what what are AMF and what are the roles that they play in ecosystems with plants?
Toby Kiers 24:57
Yeah, definitely. It's a symbiosis that's evolved between plant roots and what are called mycorrhizal fungi. So we study arbuscular mycorrhizal fungi, which are also called AMF. And this symbiosis evolved some 475 million years ago. And it's really fundamental, it's a building block to all terrestrial life, right? So even people tend not to know this, but fungal mycelium actually served as a plant root system for 10s of millions of years until plants could evolve their own, right. So actually, fungi are the ancestral state of plants, right, not roots. But as this as this, you know, the rise of these plant fungal partnerships happened in the past, it corresponded with about a 90% reduction in atmospheric co2 levels, because what was actually happening was that the plants were fixing co2 and feeding it to these fungal networks. And so now today, about 80 to 90% of all plant species form a trade symbiosis with these mycorrhizal fungi. And the fungi are providing nutrients, right, they're building these vast hyphal networks in the soil. So hyphae, they're also called mycelium, they're very fine, they're like the individual strands of kind of a spider's web, you know, thinner than a thread of cotton, but a handful of soil can contain about 100 kilometers of this fungal network. So very, very dense. So when we think about the living biomass of soils, for example, 50%, up to 50% of the living biomass of soils is these fungal networks. So these huge, you know, hugely important components of underground systems, but also incredible evolutionary dynamics between them. So they've really been a model system in our lab for trying to understand conflict and cooperation, we're really interested in the strategies of trying to understand the trade of resources between plant roots and fungal networks.
Marty Martin 26:52
That's staggering, about the the biomass of these organisms. What's the relationship with diversity? For any given plant, is most of the biomass comprised of a single species of AMF or, how many different species are we talking about?
Toby Kiers 27:07
Very diverse, very, very diverse. Yeah, I mean, it really depends on the plant and what, you know, what kind of ecosystem we're in. But anywhere from 5 to 25 different species can be on a single root system, so so pretty diverse. And then, you know, just hundreds of meters of hyphal threads that are connecting different plants simultaneously. So again, this is a very different system from an evolutionary vantage point from the legume rhizobia system, because the fungus is connected to multiple individuals at the same time. So even if one plant cuts off its resources, it's not necessarily a dead end for that fungus. And so it leads to even more interesting dynamics.
Marty Martin 27:50
In the underground network. I mean, if sort of we looked under the soil of a typical eastern North American forest, there's lots and lots of different plants above ground, but how much diversity is there below ground? And how much integration is there in the trees that are above ground, with the fungi that are below ground, sort of across species? Do, are birch interconnected with oak, which are interconnected with pine or how does that look?
Toby Kiers 28:15
Yeah, yeah, there's a bit of that there's a bit of that. So there's two real major types of mycorrhizal fungi. There's the arbuscular mycorrhizal fungi. And those tend to be associated with herbaceous plants and grasses, but also with deciduous forests, like maples and things like that. So those are all attached to arbuscular mycorrhizae. And then there's the ecto mycorrhizal fungi. And those are quite interesting because they don't penetrate into the cell. But instead, they form a hartig, what's called a hartig net on the outside of roots, and they tend to trade more nitrogen than phosphorus. And these are associated with needle type trees, your pines, your furs, but also with oak. So again, there's there's some different plant families there associate with ectomycorrhizae. And those, when you ask, when you start asking about fungal diversity, it's like, yes, right. Yes. And yes. And yes. Like it's not even worth a conversation yet, because we're so far away. I think people are saying now we've described about 10% of the, you know, the kingdom of fungi. Right? It's just such a vastly understudied diversity, that it's quite difficult to answer those questions. And so really, one of the major pushes that we're going to have in the future is trying to map out these diversity, where are the diversity hotspots, you know, what are associated with diversity? Do you have high carbon sequestration? Do you have tighter nutrient cycling in diverse communities right, trying to link diversity to ecosystem function? It's it's it's really hard how unknown it is. We just know that they're incredibly dense, like, you know, a single gram of soil, that's 90 meters of hyphal threads, right? Sometimes I try to picture it like a grassland is associated with these arbuscular ones and if you have a hectare of this grassland, it's it's the equivalent to the length of 12, about 13 million Amazon rivers, the length of that, under one hectare of grasslands.
Art Woods 30:11
Yeah, it's astonishing.
Toby Kiers 30:12
And actually, to stick with that river analogy, these networks are basically nutrient rivers. And so what we do in my group is work with a group in, biophysicists here in Amsterdam, a group that's led by Tom Shimizu at a university, an institute called AMOLF. And we are trying to quantify how these nutrient rivers are flowing. And it's really beautiful, it's, it's just stunning when you see how complex and beautiful these dynamics are under your feet. And the thing I think that makes it the most sort of visually stunning is that most fungi have what are called septa, right? Those are the cell walls that would go across and break a long mycelium into sort of different compartments. But here, it's like an open pipe system. It's really like a river. It's just, it's just an open flow with so many different junctions. And when you actually get to spend time looking at these nutrient rivers, you see that they're moving two directions at the same time.
Marty Martin 30:12
Yeah.
Toby Kiers 30:21
Even I'm stunned just saying it, right, it's like, it's like an anti parallel movement in a single pipe. So, and of course, it makes sense, right, the carbon has to be going one way, away from the root towards the growing tips. At the same time, the phosphorus and nitrogen have to be going the other way. So you get this anti, bidirectional movement of different nutrients streams in a single pipe. So that's why we're working with physicists to try to understand how the fungi does that how it controls these flows. And not only is it moving two directions at the same time, but it has this dynamic nature to it where entire flows will go all the way to the left, and then they'll switch directions and then go all the way to the right. And you're following these particles inside these nutrient rivers to get some kind of indication, some kind of way of quantifying what's going on in there. It's like trying to learn a new language with, there's no dictionary right? The fungus is moving these resources in a way that we're trying to understand.
Art Woods 32:18
You need your fungal Rosetta Stone here to break this all down.
Toby Kiers 32:21
Exactly.
Art Woods 32:22
Well, I want to dig into the details of how phosphorus moves in these these networks and focus that on your recent paper in Current Biology. But before we do that, can you just say how do these things actually move inside these pipes? Like if nutrients are moving along, what's moving them?
Toby Kiers 32:37
Yeah, what's moving them? Exactly. That's exactly what we're trying to figure out. So it looks like there's some, some form of molecular motor that is running along tracks on either side. And you can kind of see this at cross sections where the hyphae splits and some particles will go one direction. Yeah, just like how you would have tracks on a railroad. And if they're on different sides of the tube, and one tube has a junction and takes a turn, you can kind of follow that track and that particle down a different path.
Art Woods 33:10
And so are these like motors crawling along microtubule networks?
Toby Kiers 33:13
Exactly.
Art Woods 33:14
And do we know what the molecular motors are?
Toby Kiers 33:17
We don't. I mean, how can this be the most ubiquitous symbiosis on Earth is what we say, and we have no idea how the nutrients are moving. But yeah, molecular motors microtubules, you know, we can we can say these words, but actually, you know, the true dynamics of the loading and unloading is not known now. And it's more than just molecular motors, because we are observing speeds that go way beyond what a molecular motor can do. And so there's also some sort of contribution of pressure, there's a pressure driven bulk flow at the same time, and how that is under control of the fungi is really interesting, right? Because it's a pressure, and we know that these these networks, they provide a lot of water as well, right? So they are, so there's definitely pressure, a very important pressure component. But you can imagine, you know, I say, oh, we should know by now. But actually, it's it's really hard to study these networks in the lab, because they are what we call obligate biotrophs, right, big word, but all that means is that the fungi are obligately dependent on the root system for all of their carbon. So you're not, you're bringing in the whole system into the lab, you need to grow the root at the same time as the fungal network. We can't just grow fungi.
Art Woods 34:34
Maximizes your experimental pain, right?
Toby Kiers 34:36
Yeah, exactly.
Art Woods 34:37
Yeah. So before we move on, so I'm really intrigued by this idea of water flow and pressure, pressure driven flows of particles, because that would seem to contradict this idea of bidirectional flow, right? You can't have,
Toby Kiers 34:49
Sure does.
Art Woods 34:50
Pressure waves going in the same same in opposite directions in the same tube?
Toby Kiers 34:54
Exactly, but you'll see these bursts of pressure where the, where it looks as if the entire cytoplasmic contents are moving in one direction, and then it will, it will stop. And then you'll see kind of this background molecular motor potentially going, and then the pressure will start again. I really I invite you, I invite you to look at some of the videos of this, of these flows.
Art Woods 35:19
I have, on your website, and they're stunning as like, just just really amazing.
Marty Martin 35:24
Yeah, they are amazing. It makes your brain hurt, like Art's saying, and I mean, how in the world is that possible? It doesn't, doesn't look real at all. Have you gotten to the point yet of having the chance to ask about efficiency? I mean, if that even makes sense, because yeah, it's just so bizarre that they can reverse. How far are they away from the optimal of doing such a thing, although we don't have a lot of precedent about doing such a thing, so maybe optimal is crazy.
Toby Kiers 35:49
Yeah, exactly. It's, we try to avoid the words, you know, maximizing and optimal because with these guys, we really can't, we can't we can't tell what their state is, so to try to measure against that is difficult. But it's a great question. I was giving a talk in Princeton, and I was showing these videos and showing how much the fungus seemed to be moving the contents within its hyphae back and forth. And there was a scientist in the audience, Howard Stone, who is brilliant biophysicist that studies these types of dynamics. And he was asking if the fungus does this, you know, to calculate, to help calculate what resources are actually inside that fungal network. So you can imagine that it's very different, soil is incredibly heterogeneous. So you've got hot patches of resources and very low resource patches, and the fungus has to basically be able to understand where to move those resources to maximize their gain. And so does it help to then sort of move the resources around in the network to get some kind of calculation of how much is available and how that would change your strategy. So that's something that we have, you know, one of these interdisciplinary grants to try to understand is, is the fungus sort of actively, it's definitely using a lot of energy to move these resources around. And we've got some very cool experimental evidence suggesting that yeah, it'll move phosphorus from one side of the network across to the other side to increase its carbon gain from the host root. So rather than trading locally, it moves the phosphorus around to a place where plant demand is higher and gets more carbon for it. But how does it calculate that?
Marty Martin 37:29
Wow.
Art Woods 37:29
Yeah, super smart. Let's just dig into this this paper that I keep mentioning the Current Biology one. So this is a, I think, 2019 paper led by Matthew Whiteside. And you guys did this, what appears to me to be just super clever thing of developing a nice experimental technique for measuring where phosphorus goes, and then manipulating relative levels of phosphorus availability as a way of trying to deduce the rules by which the hyphae are moving phosphorus around. Let's just start with the experimental setup, which I thought was really amazing. So you had these sort of arenas where you can put plant roots and hyphae and differences in phosphorus. So can you just describe the layout of that experiment?
Toby Kiers 38:13
Of course, so we had a triple compartment petri plate. So again, what we can do in this symbiosis is we can grow the fungal network with a root system that doesn't photosynthesize. So this makes our life a little bit easier, because the root system can take up carbon directly from the media and then put it in a form that is, that it can feed to the fungus. So the fungus has no access to that carbon, but the root system is keeping it alive by feeding this fungus. And so then we colonized that root system with a large fungal network and had it grow into these two separate fungus only compartments. And that's very important.
Art Woods 38:51
So the roots just can't get into those those compartments?
Toby Kiers 38:54
Exactly, so you can imagine the root staying in sort of the upper, you know, top third of the petri plate and the fungus growing down into the other two halves. And that's where we added this tagged phosphorus. And so took us a few years working with with Matthew Whiteside, to develop this fluorescent technique that relies on quantum dots that basically produce very pure bright fluorescence when hit with a UV source. Depending on the core inside these quantum dots, they emit different wavelengths. So basically, you can tag something like phosphorus with different colors, depending on what quantum dots you add. So it allows us to track phosphorus across the network
Art Woods 39:40
Right, and once the phosphorus from different sources starts to mix, you still can distinguish based on the wavelength of the fluorescence.
Toby Kiers 39:46
Exactly. So we were using something called apatite, which is a rock form of phosphate that the fungi are good at taking up into their hyphae, and then transporting it, and so we were using either red tagged phosphorus or this cyan color tagged phosphorus, and then as you said, we set up three different treatments. So either the resources were very even across the fungal network, so they were spread 50 50, or they were spread in amount where one patch was higher than the other, so it was 70 30, or it was very extreme are where we put 90% of the resources in one compartment and 10% in the other. And because those resources were labeled with different colors, we could track where they went and how they were traded with the root system.
Marty Martin 40:32
So drumroll, tell us what happened there, this is intriguing.
Toby Kiers 40:37
So what we found was that inequality in these resources, right, when there was really extreme inequalities of 90% of the resources on one side of the fungal network, compared to 10, the first thing it did was increased trade, right. So what does that mean? It's so interesting, so somehow, when the resources are homogeneously spread across the network, trade was at a certain level. As soon as you increased that resource distribution so that one side had higher than the other, that stimulated the plant to give more carbon. But what happened actually, it's not that it just overall gave more carbon, but instead, what we found was that it was giving more carbon to the resource poor side of the fungal network. So actually, that was complete opposite of what we had expected, we just expected the resource rich side to get bigger and bigger, with more carbon being sent to that side. But actually what was happening, we found that because we tagged the resources in different colors, we could see that it was first going over to the resource poor side where it was then traded. And because of that, it was getting more carbon per unit of phosphorus, the plant was providing more carbon per unit of phosphorus where resources were low.
Art Woods 41:52
So basically, the per unit cost of a phosphorus molecule goes up for the plant when phosphorus is poor, and the hyphae are exploiting that by shuttling the phosphorus to where it can get a higher price for them.
Toby Kiers 42:06
Exactly. So that's why it's quite interesting when you ask questions about efficiency and things, right, because it does, that's an energy intensive process to move it across, and so again, we really want to understand this in a, you know, we can try to understand it in sort of a you know, with an economic perspective. But again, it's an observation, right. And it was, when you do these experiments, they have to be like achingly precise, right? They're just, and they take a really long time to set up. And they take a really long time to analyze. But that finding was really striking. We were very surprised.
Marty Martin 42:40
Well, so I'm trying to find out, maybe it comes down to the nuance of the experimental design that I missed, but isn't another way to say this, that the plant is willing to pay a higher cost to a mycorrhizae that sort of has its of less quality, it's more at risk? I mean, is the plant fully connected to all of the mycorrizae? Or is it not really able to access both the low and high phosphorus conditions?
Toby Kiers 43:04
Right, so it's not ever able to access directly the low and high phosphorus. So it's only able to get the phosphorus through the fungal network.
Marty Martin 43:12
Okay, well, why should it ever pay a higher cost? I mean, wouldn't you expect the sort of evolution of a position where the plant's just not gonna pay that? Or is that just not an option? It always needs phosphorus, there's no other source for it, it's still gonna pay this high cost no matter what?
Toby Kiers 43:25
Exactly. I mean, that's what we're trying to understand. So you can kind of think the modularity of it, right? Like, how connected is it? It's about two organisms trying to sense their strategies over spatial and temporal landscapes. And so yeah, this was just sort of one experiment where it definitely it was very clear that more carbon was going to the fungus on this side. But yeah, under, you know, when we look out in nature, is the same thing happening? You're talking about this tiny little root system with no photosynthetic top, in a petri plate. So really, for us, the big frontier is trying to do these types of experiments out in nature, because so many things could be different, right? And you're exactly right. Like maybe the plant has evolved to say, okay, no, I, if I can keep getting phosphorus on this side, I'll be the one to take it on this side, and then I will move it across. So again, it's it's really about scaling. And so what our biggest I think our biggest frontier in this field is trying to take these very small scale experiments in petri plates and ask is the same thing happening in nature?
Art Woods 44:27
Yeah, let me ask a related question, and this circles back to something you said just a few minutes ago about the costs of transport across these hyphal networks. As I am envisioning it, these petri dishes that you were using in the experiments are pretty small, and we're talking about hyphae moving things, you know, a number of centimeters. So at some point, presumably, the costs become prohibitively large to move resources, many meters or 10s of meters. And so is there a limit to how far these hyphal networks would be willing to move resources around in order to get the best price?
Toby Kiers 44:59
It's almost like you're reading off the script of my lab meetings.
Art Woods 45:04
You've been hacked.
Toby Kiers 45:06
It's exactly what we're trying to figure out now right is, so we're, I mean, working with biophysicists is, you know, for any biologist, right, I would definitely suggest some interdisciplinary, just go for it because I have learned so much about not only sort of, it's just such a different perspective, but the tools that they have available are just mind blowing. So we, as I said, I work with Tom Shimizu. And we have this incredible postdoc named Loreto Galvez, and she's built an imaging robot that basically allows us to track the growth of these networks in sort of 4D plates simultaneously across any kind of artificial landscape we want to make, and then hone in on the flows right? Inside those networks, so you've got this topology, which is like your trade network. So that's exactly why I'm interested in your question Art, because you've got this trade network, and then you have to figure out is that, at what point is it no longer efficient to be moving it towards this root and instead, maybe transferring it to another root? Is there some sort of absolute level, where,
Art Woods 46:09
It sort of sets up the spatial scale of this movement, right?
Toby Kiers 46:15
Exactly. So it's not only a spatial scale, but like, we're looking, what's cool about these networks is they can also fuse together, it they're genetically like, right? They don't even have to be the exact same genotype, they just can be close genotypes, and they can fuse and then there's all of this resource sharing and these cross linkages. And so again, you can imagine that if a if a network is growing out, these cross linkages can really help it move resources to increase the efficiency to get those back to the host plants. But we're trying to figure out sort of the symbiotic rules of topology, right? What is the what is, what does it mean to be a symbiotic network? It's different than a free living fungi, right? It has to do different things. It has to calculate different things. And it has this one sort of hub that it has to get to, its resources to, which are the roots. And of course, those can vary in space, but how does that change the way it builds its topology, and then how does that change how the flows happen inside that topology?
Marty Martin 47:08
Right. Do you know anything, in the petri dish setups, do you know anything now about how the networks are gauging inequality? I mean, that alone is pretty compelling. And I would think if it's ever going to be tractable, you better start there.
Toby Kiers 47:20
Yeah. Yeah, exactly. Yeah. So these poor fungi, we, you know, we kind of put them through the wringer. Right, like we try to do all of these manipulations and see how they respond. And it's all just kind of a work in progress. I mean, again, these things are very difficult to, to grow and to follow over time. And if you even just follow one, I mean, we've got a PhD student who's following even just one network over time, and you're getting into the hundreds of 1000s, even millions of nodes that he's trying to track simultaneously. So we're getting terabytes of data on these network structures, and then trying to sort of decode why are they doing what they do. And this is the this is really important that it's time resolved, right? So of course, we can grow a network and say, okay, this is what it looks like now. But because we're taking images every four hours, you're literally watching the building of a road system, but decoding those terabytes of data has turned out to be difficult.
Marty Martin 48:19
Tricky.
Art Woods 48:21
I want to I think, I think we're gonna jump and sort of try to generalize some of these trade rule arguments you're making and apply them to human systems. Before we go there, let me just ask one more question about currency. So we've talked mostly about phosphorus and nitrogen trading, are there other more obscure things that the plants need that the fungi can access? You know, are other, you know, 10s, or hundreds of currencies that are involved, or are nitrogen and phosphorus really the main ones?
Toby Kiers 48:48
Yeah, not 10s of hundreds, but they definitely, the fungi are linked with many more benefits than just nitrogen and phosphorus. So for example, we know that they're important in heavy metal tolerance, right, they can actually sequester heavy metals, we know they're very important in water uptake, as I said, so incredibly important in water relations, pathogen protection, and as soon as you start getting into pathogen protection, right, like the secondary metabolites, that's, I guess, when you get into the 10s of hundreds of, you know, potential interactions that this could lead to. And so yeah, it's not really the focus of our group, but there's really compelling evidence that when the connection with these fungal networks is made, that that really helps plants up regulate their own defenses, and some of those times that actually that upregulation produces secondary metabolites that may be even traveling across the network. You know, I always say it's not, it's not plants necessarily warning each other because that shows intent, but they could be picking up on cues that are passively leaking across the network, for example. So I think that's a very different way of thinking about it.
Art Woods 49:53
Yeah, that's sort of information flows, yeah.
Toby Kiers 49:55
Exactly. And so it's picking up on cues. It's eavesdropping on your neighbors because you are connected, right? And so if a plant does get attacked, it will upregulate its defenses and whatever response that may have, that impact could be felt across the fungal network.
Marty Martin 50:21
So how do we think about these observations in the context of human economics? These systems have had millions of years of practice, are there consultancies out there now using evolutionary thinking to improve portfolios?
Toby Kiers 50:35
Yeah, so that's always really hard to, you know, use these fungi as analogies for humans. And, you know, I think we can ask some potentially useful questions. I'm not sure how, you know, I like asking questions and not sure how useful the answers are. But like in our lab, we can really we can figure out like, what drives economies to break apart, right? If there's a symbiosis, like, how can we perturb the system that it's no longer useful to both partners? You know, we can ask how do small local markets evolve in these systems, again, because it's a physical movement of resources, which is a bit different than our economy now, but you can ask about like optimal, you know, there I am using it, but what size the number of trading partners that actually increases market exchange. So there's some theory coming out of our group that like, if you have more fungal partners, that actually may be very positive for plants in terms of phosphorous uptake, because they're competing simultaneously to provide and potentially undercutting the cost of phosphorus. And so that's actually pretty useful in like sustainable agriculture, right, instead of just having a root system, inoculated with one fungi, but instead have these sort of diverse, healthy communities where competition may benefit the plant in terms of how much phosphorus is provided. You know, it's nice, we can bring an economic system into the lab, we can watch these trade strategies evolve, we can study tipping points, right. And, you know, if we really push sort of sci fi, then yeah, we can try to understand the algorithms of the fungal trade, because they're decoupled from any kind of emotion. They're decoupled from any sort of anticipation, and they've been under selection for hundreds of millions of years. So there is something about if we can figure out the trade algorithms and the way that the networks form in terms of efficiencies, then that could be helpful, I think, in the future.
Marty Martin 52:25
Well, I mean, I'm probably a biased perspective here. But that all makes sense. And the other piece that seems conspicuous to me, that I would imagine is difficult in sort of basic human economics is the tractability of your system, that you can do experiments with a network, right, an evolved network even, that will allow you to get traction on what for human economies is going to be so many other things not just to mention the cognitive dimensions about how those operate.
Toby Kiers 52:49
Yeah, definitely. And the fact that we can use, you know working with quantum dots is very tricky, and so it's not the easiest experiments to set up. But now we're up to three colors simultaneously. So you can also do things over time, right? You can add different colors at different times, so that gives us a nice temporal resolution. And again, yeah, you can do some spatial things. So it's definitely it's, it's opening up sort of that black box of trade. And instead of just saying, okay, the before and after, now we can kind of look at the interesting strategies in between.
Art Woods 53:21
Let me stay with the sci fi theme here for a second and ask about parallels between the way the internet works and the way these fungal hyphal networks work. So from your perspective, I guess the way to ask this is, are there insights to be had for the worldwide web from studying the wood wide web? Is, is there anything there?
Toby Kiers 53:43
Yeah, well, okay, well, first, I tend to be a little bit shy about using the term wood wide web, mostly because I really want to get across this idea that these guys are everywhere, right? It's not just in woody systems, they're in grasslands.
Art Woods 53:56
Yeah, fair enough. Okay, I'm just making a dumb joke here, but let's just go with it.
Toby Kiers 54:01
No, but the other thing that I, why I'm harping on this is that when we use analogies to the internet, then these fungi come across as passive accessories, and if there's one thing I've tried to make clear, you know, throughout my research career, it's that they're anything but passive, right? They are actively moving these resources and evolving strategies to help them reproduce. And so it's hard to compare, like, of course, at the most superficial level, topology. As soon as we, I mean, when you, we're talking about these, these networks, and how we're using this imaging robot, and it's all nice and good, but that's we're still doing it on a 2D plane. As soon as you know, you've got, we've got a grant now to start doing more like 3D X rays of these types of things because then I think the topology will become even, you know, terabytes of data in an hour right? It is a bit it is so dense and it is so complex, and we've been really limiting it to growing on a single plane. As soon as we go into that 3D space, I think we're going to learn a lot about topologies of efficient networks.
Art Woods 55:11
Yeah. So just if I can articulate your objection to this idea of analogizing these things, in the world wide web, the wires that are connecting all of it, the fiber optic cables are just passive participants. They're links between nodes. And what you're saying is that the difference in these fungal networks is that the wires themselves have interests and evolve strategies and physiologies that are changing the network. Okay.
Toby Kiers 55:36
Yeah, exactly. And that, it's a living network, right? That's fantastic, right? When we talk about the internet, it's us that are laying these cables and trying to decide where to go. But this network, it's, it's, yeah, it's under selection. And so its body is its topology. And so that, that I think, can lend an even more interesting perspective on network theory, because there's nothing passive about it.
Marty Martin 56:01
Okay, so then that makes sense Toby, about your recent effort that went to this new nonprofit, called SPUN, the society for protection of underground networks, to, you know, collect the data and maybe shift the mindset to thinking about living networks, as opposed to other versions of the world wide web. I gotta say that, well, first, the webpage is just absolutely amazing. We've already alluded to the cool videos, which are there, among other things, it's a striking page, but it lists out a lot of the ambitious goals that you have. And I guess one of them, maybe the most prominent is to map all the fungal networks on the earth. How are you going to do that? And how long will that take?
Toby Kiers 56:38
Yeah, yeah, so again, we have to clarify that what we're trying to do is map the biodiversity. So not the physical topography, not yet, not yet, right? We're gonna start with like a, we're gonna start with a millimeter by millimeter of soil, but actually mapping the biodiversity hotspots and the biodiversity in general hasn't been done. And for us, that's just shocking. So these fungal networks, they've really been, I think, a global blind spot in conservation and climate agendas. At the minimum, we know that they're moving about 5 billion tons of carbon from the atmosphere down into plants and into the fungal networks. If these fungal networks disappear, then we're losing a really large carbon sink. So yeah, our aim is to actually try to start mapping where exactly these fungal networks are. And we do that by sending out what we're calling myconauts, right. Are there places on the planet that you think are deserving a particular attention where we've just not put the effort before and something about the climate suggests that there's a lot of diversity there?
Marty Martin 57:33
I love it.
Toby Kiers 57:33
Myco, meaning fungi, and naut meaning explorer, and working with local communities to actually sample the soil systems in some of these most remote areas and areas that are facing, you know, expansion from agriculture or deforestation, but are predicted biodiversity hotspots. And so we have to get in there fast and figure out what networks are there and sort of what they're doing. Yeah, definitely. So it's not even that I think like it's yeah, there's, I know, because what we're doing right now is we're working with global fungi, which is an open source platform, where fungal reads are deposited on, when papers are published. And so using about 10,000 global samples from their database, we made the first predicted biodiversity hotspots of both the arbuscular and ectomycorrhizal fungi. And they're surprising. So I think one of those maps is up on our website at SPUN.earth, and we've identified about 10 biodiversity hotspots that we really need to move fast on, places like Siberia, right, where you, you know, it's different than let's say, you know, the Amazon actually looks like it might have a biodiversity hotspot as well. But places like grasslands that you're not expecting, you know, above ground biodiversity to be so high, but actually below ground biodiversity is really high. So we're trying to kind of cause a mind shift, right, that if we know that, I think the current estimate is 25% of all species on earth live underground, right? So there's this huge biodiversity underground, but yet, we're not conserving those ecosystems for what they hold below ground. And I think we'd have actually a shift in sort of some conservation priorities if we can identify these biodiversity hotspots. And someday we actually imagine that you can have, you know, a conservation easement based on biodiversity below ground alone, right. And so it might not look like a lot above ground, but we know that this is a hotspot and so, yeah, we're really advocating for a big mind shift.
Art Woods 59:44
So in terms of disturbance to fungal networks, what would you say are the major factors that that are causing them to serve, is it changes in land use? Is it you know, invasive plant species coming into new areas? Is it climate change itself?
Toby Kiers 59:58
Yeah, keep going. Keep going, they're all.
Art Woods 1:00:00
It's just, yeah okay. Okay, all of those things? I mean, but do we know what the worst thing is?
Toby Kiers 1:00:04
Well, we're particularly worried about agricultural expansion I mean agriculture is really harsh on these communities, not only because of the chemical inputs, you know, fungicide right, but tillage, right? Tillage is really harsh in terms of these networks that can select for kind of this weedy mycorrhizal fungi that, you know, don't make these sort of robust, thick networks. And yet, we know that up to 80% of a plant's phosphorus can be supplied by these fungal networks. So it's like, it's this life support system, but at the same time, our current practices are really destroying them. So yeah, so we're worried about agricultural expansion, you know, obviously, logging has really negative impacts, there's some data suggesting about, you know, when you compare logged plots to unlogged plots, about a 95%, decrease in abundance of these networks, right. And they come back, they're resilient, right, they can come back, but not always the same levels of diversity. And sometimes it can take decades. And so, you know, basically trying to get enough data to inform practices like logging, like, okay, you know, if you leave 10% of the stand that's associated with, you know, 50% decreases in diversity. But if you leave 25% of a stand, then that, you know, may some support 75%. So we want to be able to provide metrics to, you know, managed ecosystems, so agriculture and logging, and so that we can actually yeah, add this to sort of the one of the reasons that we need to really lead different management practices that sort of take a fungal centric point of view.
Marty Martin 1:01:35
So, Toby, for the folks that are listening to this, are there things that they can do? I mean, presumably, there's a lot of information on the website. But is there something else that you would advise?
Toby Kiers 1:01:45
Yeah, of course, like, so. When I see bare soil, right, it's like seeing a naked person, you got to cover up the soil. I sometimes see it and I think just cover it with leaves and plants. Obviously, these networks get fed by plants, so native plants are always very good. Just don't leave your soil bare, don't use chemicals, even things like Roundup, right. I mean, in Europe, it's outlawed. It could be very, very bad for for these networks. There's data on some of these very common chemicals that people add to their lawns. But also in urban environments, right, advocating for things like living roofs, for green roofs, this is very surprising, but actually, the, there's some beautiful data that suggests that these spores spread aerially, in the air, right. As long as you can keep kind of a green corridor for these spores to spread, you'll help keep that conductivity through cities, you know, so we're very anti concrete and things, but if we put some green, some living green surfaces through cities that can really help. And again, I guess we're promoting this idea that, you know, we're building up the pipeline where people can help us by sampling in their neighborhoods,
Art Woods 1:02:53
Yeah, so if you get people helping, I mean, this, so SPUN just sounds really grand and really awesome. If people want to get involved, what should they do?
Toby Kiers 1:03:01
Yeah, so definitely, what's the easiest is to is to go to SPUN.earth and join. We're, we're just gathering names and and starting to train myconauts. You know, that's definitely what we're trying to do. Our goal is about 10,000 samples in the next 18 months. We're still at very early stages, you know, we just got a big founding sort of capital to help us get up the open access system. And it's going to be a little bit of time before people can send in soil samples still, but we're working a lot with different research programs that are already doing lots of sampling and have already extracted some of these communities and trying to get them to to upload as well. So just we're really trying to get a global picture of these fungal networks and and they can they can help by advocating and joining.
Marty Martin 1:03:47
Excellent. Well hey Toby, we're sensitive to your time. This has been an absolutely fantastic conversation. I have learned a ton and it's just really cool work. We wish you the best with SPUN, we're looking forward to hearing more about it. But we always give our guest the chance to sort of have the final word. Is there anything else that you would like to say that we didn't ask you?
Toby Kiers 1:04:06
It's like, it's like when you're asking me who my favorite scientist is.
Art Woods 1:04:11
You could just take a pass.
Toby Kiers 1:04:13
No yeah, I really, I had a wonderful time talking to you both today. So thank you so much for having me on.
Art Woods 1:04:20
Yeah. Thanks Toby, really loved it.
Toby Kiers 1:04:21
Thank you so much.
Marty Martin 1:04:31
Thank you for listening to the episode. If you like what you hear, let us know via Twitter, Facebook, Instagram, or leave a review on Apple podcasts. And if you don't well, we'd love to hear that too. All feedback is good feedback.
Art Woods 1:04:42
On the next episode, we talked to Henkjan Honing about the origins of musicality. Are animals able to perceive the beat and other elements of music like pitch and tone?
Marty Martin 1:04:51
Thanks to Steve Lane, who manages the website and Ruth Demree for producing the episode.
Art Woods 1:04:54
Thanks also to Brad van Paridon for writing the script, and Jordan Greer, RB Smith, Natasha Dhamrait, and Kyle Smith for helping to produce the episode. Keating Shahmehri produces our awesome cover art
Marty Martin 1:05:04
Thank you to the College of Public Health at the University of South Florida the College of Humanities and Sciences at the University of Montana and the National Science Foundation for support.
Art Woods 1:05:12
Music on the episode is from Podington Bear.